The present invention relates generally to optical switches and in particular to an optical switch utilizing a fluid media having an index of refraction matched to a contiguous light scattering layer. When the fluid contacts the optically scattering material, their interface becomes virtually transparent. Embodied in a solar collector, the optical switch, when activated, removes the fluid media, thus turning off the collector until a satisfactorily low temperature is achieved.
Solar thermal energy converters have been proposed as viable alternatives to petrochemical and similarly conventional home heating means. Manufacturers of lower temperature home heating solar collectors have continually sought lower cost alternatives to improve the cost effectiveness of solar energy vis-a-vis conventional heating techniques. An approach taken by a number of solar panel manufacturere is to substitute plastic components for the more costly copper and other metallic components. Substituting plastic components saves both on cost of producing the panel and on the weight of the panel. See, for example, U.S. Pat. Nos. 3,918,430 and 4,046,135. Although plastic components may readily be substituted for many typical collector parts, these plastic components conventionally have upper working temperature limits in the general operating temperature range of the collector. These plastic components function adequately under normal collector system operation. However, in the instance where the collector's heat transfer means is interrupted, the temperature of the collector rises substantially. The temperature in a conventional flat plate collector, in the absence of heat exchange means, may exceed 150.degree. C. A limited number of plastics can withstand these temperatures, and plastics capable of withstanding these temperatures are generally more costly than their metal counterparts. These devices may be generally categorized as employing either mechanical means to expel unwanted heat from the collector, or optical means for reducing the amount of light absorbed by the collector. The present invention relates to this latter category, that is optically inhibiting light from reaching the solar collector.